System of motor control



Feb. 12, 1935. c. J. WERNER SYSTEM OF MOTOR CONTROL 2 Sheets-Sheet llNvENroR Ca/Vz'n J Tf1/erna Y BY Ar-roRNEV l 6 Mu Filed March 22, 1933may Nv//Y Tir/mo Feb. l2, 1935.l

C. J. WERNER SYSTEM oF MOTOR CONTROL Filed March 22 2 Sheets-Sheet 2INVENTOR Patented Feb. 12, 1935 1,991,040

UNITED STATES PATENT OFFICE 1,991,040 4 SYSTEM OF MOTOR CONTROL CalvinJ. Werner, Dayton, Ohio, assignor,v by

mesne assignments, to General Motors Corporation, Detroit Mich., acorporation of Delaware Application March 22, 1933, Serial No. 662,029

6 Claims. (Cl. 172-279) This invention relates to alternating currentwinding 26 are also surrounded by a third windmotors and moreparticularly to a system of ing 30 which is eiiectively magneticallycoupled starting and controlling single phase alternating with the rotorand preferably with only the current motors. auxiliary winding 26, sincethe coupling between 5 An object of this invention is to provide a thewinding 30 and the ends of the main held 5 reliable and durable controlsystem for single winding 24 is substantially neutralized by virtuephase alternating current motors. of the substantially equal couplingwith both Another object of this invention is to provide ends of thewinding. The reduced effective magan electrically operatedcontrol systemfor connetic coupling between the main winding and l trolling thestarting and running circuits of the third winding is preferable, sinceit is desir- 1o single phase alternating current motors. able to obtaina large percentage change in the Another object of this invention is toprovide controlling voltage. lFurthermore, the circuit a' control systemfor single phase alternating to the auxiliary eld winding circuit isopened current motors that will compensate, within a after the motorisstarted, so that a reduction l reasonable range, for variations in linevoltage. of rotor speed due to an overload or reduction i5 Anotherobject of this invention is to provide of line voltage permits theswitch to be more an electrically controlled system for controllingeasily actuated to the start position. the condenser circuit of acondenser'start type A power supply line wire 32 is connected to of asingle phase motor. the main eld winding 24 and to the auxiliary Furtherobjects and advantages of the present field winding 26. Another powersupply line 20 invention will be apparent from the following Wire 34 isconnected to an electromagnet 36 description, reference being had to theaccomwhich, in turn, iS Cfmheted by a Wire 38 t0 the panying drawingswherein a preferred embodimain eld winding 24. The third winding 30 isment of one form of the present invention is connected by wires 40 and42 to an electromagclearly shown. net 44, and is also connected to theauxiliary 25 In the drawings: held winding 26. The electromagnets 36 and44 Fig. l is a wiring diagram of the stator of are provided with cores46 and 48 respectively,

a motor vadapted to be used in the present inwhich cooperaterespectively with lever arms 50 vention. and 52 of a common armature 54,which arma- Fig. 2 is a wiring diagram illustrating the ture is providedwith bifurcated arms 56 and 58 30 circuit connections of a systemembodying the Which` straddle respectively bfuleated arms 60 presentinvention. and 62 of the base 64, as shown in the diagram.

Fig. 3 illustrates by curves the variations in The armature 54 iSmaintained yieldingly either pull of the electromagnetic switchcorresponding in a DOStOrl iIiClned toward the Core 48, or inv tovariations in the speed of the rotor. Clined tOWard the COTE 46, by aSpring 66 COD- 35 Fig. 4 illustrates by curves the variations in neetngthe armature 54 with the base 64, and so the induced electromotiveforces and current in arranged that its center line of action moves tothe electromagnets of the electromagnetic switch either Side 0f aVeltCal P13118 through the Center corresponding to variations in thespeed of the lines Of the arms 56, 58, 60 and 62. The armarotor.v ture54 has a contact carrying member 68 40 Fig. 5 is a fragmentary elevationof an asmounted thereon and carrying the contact 70, sembly embodyingthe present invention, and Which COIlaCt iS ehgagable With a COODeTatnesome of the parts thereof are shown in section. Contact '72. A condenseror a reactance 74 is Fig, 6 is a fragmentary view with part Cutconnected to the power supply line wire 34 andv away'to Show a, Sideelevation 0f the electrol() the Contact 72. The COIIaClZ 70 S COnneCted45 magnetic switch, through the contact carrying member 68, arma-k Fig.7 is a fragmentary view showing the top ture 54, spring 66 andbifurcated arms 56, 58, of the electromagnetic Switch, 60 and 62 to thewire 42 and the common con- With particukureference to Figs. 1 and 2,nection between the auxiliary field winding 26 the electric motorcomprises a squirrel cage rotor and third winding 30. Hence, when thecontacts 50 20 in cooperative relation with a stator 22 having 70 and'72 are engaged a circuit is completed teeth such as 28 upon which amain iield windfrom the power supply line Wire 34 through the ing 24 andan auxiliary field winding 26 are condenser or reactance 74 and thosecontacts to arranged as shown in Fig. l. Stator teeth surthe auxiliaryeld winding 26 to establish a rounded by a section or part of theauxiliary starting circuit. When the contacts 70 and 72 are disengaged,the circuit to the auxiliary field winding is opened, and the runningcircuit established. o

When the power supply circuit is closed through a switch 31, theelectromagnet 36 is energized by virtue of its connection to both sidesof the power supply line through the main field winding 24. At theinstant prior to starting, only a small current is induced in theelectromagnet 44, since at that instant the rotor is stationary,v andsince without rotation of the rotor there will be no rotational voltageinduced in the third winding 30, although there is a small transformervoltage induced after the circuit to the auxiliary winding 26 is closed.Therefore, regardless of the voltage impressed upon the main eld winding24, within reasonable limits, the electromagnet 36 will attract thearmature 54 and thereby bring about engagement of the cooperatingcontacts 70 and 72. Engagement of these contacts is facilitated andaided by the spring 66 when it crosses the center line of the bifurcatedarms to the side toward which the armature is moved, and tends to closethe contacts witha snap action. Engagement of thev contacts 70 and 72closes the circuit between the power supply line 4wire 34 and theauxiliary field winding 26 through the condenser or reactance '74..

Since the circuit between the power supply line wire 34 and theauxiliary field winding 26 is formed through a capacitive reactance, andthe circuit to the main field Winding 24 from a power supply line wire34 is substantially direct, a phase difference is produced betweenthemain and auxiliary field windings; that is, the current in the auxiliaryfield winding 26 leads that in the main eld winding 24. After engagementof the contacts 70 and 72, the pull of the electromagnet 36 upon the arm50 of the armature 54, together with the urging force of the spring 66tends to maintain engagement of the contacts. The circuit thus formed inthe main eld windingv 24 and the auxiliary field winding 26 togetherwith the position of those windings, causes`the rotating field to beproduced that starts the rotation of the rotor 20.

A rotational voltage is induced in the third winding 30 by virtuel ofits magnetic relation with'the rotor. field, and the rotation of therotor. Referring to Fig. 4, it will be noted that as the rotor speedincreases, the current ofv the electromagnet 36 decreases, while theinduced electromotive force in the third winding 30 increases, asrepresented by the curves A-B and .C-D respectively. Consequently, thepull effected by the electromagnet 36 upon the armature 54 decreases asrepresented by the curve M-N in Figf3; While the pull'effected by theelectromagnet 44 increases due to the increased voltage induced in thewinding 30 due to the increase in rotor speed, and as represented by thecurve P-N at a certain critical speed, such as that represented by thelines -yrin Figs. 3 and 4, the force exerted upon the arms 50 and 52 ofvthe armature 54 is substantially equal, and an increase in speed abovethat value will result in the armature 54 being moved into a positionsuch as that indicated in Fig. 2, with the armature 54 attracted by theelectromagnet 44.

Thus, the contacts 70 and72 will be thereby disengaged, and the circuitfrom the line wire 34 to theauxiliary eld winding 26 opened. The rotor,

at the time of the opening of the contacts '10l and 72, shall havereached a sufcientlspeed lio produce its own rotating eld by virtue ofthe transformer and rotational voltages induced therein, and the runningcircuit thereby established.

Referring again to Figs. 3 and 4, it will be Anoted that when the switchis thus in the run position, and the rotor is rotating at a speed abovethat indicated by the line :r--y the voltage induced in the thirdwinding 30 which effects the energization of the electromagnet 44 isless than when the switch is in the start position, and the rotor speedis below that indicated by the line .fcy, as represented by the curve`lil-li. This isdue to the opening of the circuit to the auxiliary eldwinding 26, with which the third Winding 30 is magnetically coupled.However, the electromagnet 44 exerts a greater force upon the arm 52 ofthe armature 54 than the electromagnet 36 does upon the arm 50, asrepresented by the curves Q--R and S-T. This is due to thecharacteristic variations in the force of the magnet with the distancefrom the magnet.

With reference to Figs. 5, 6 and '7, the electromagnet switch shown, andillustrated diagrammatically in Fig. 2, is the subject matter of acopending application, Serial No. 642,158, filed November 11, 1932, andis explained there in detail. Since the principal elements of thestructure and the operation of this switch have previously beendescribed herein, and similar reference numerals apply to similar partsin Figs. 5, 6 and 7, no further explanation of the details of thisswitch will be given with reference to the latter figures. 'I'he base 64of the switch is secured to brackets and 82 by screws 84 or othersuitable fastening means and is insulated therefrom by insulatingwashers such as 83 and 85. A housing 86 having a removable cover 88 andside walls 90, 92 and 94 preferably formed of sheet metal, has a support'member 96, preferably of linsulating material, supported by the sidewalls 92 and 94, to which support.

member the brackets 80 and 82 are secured by rivets 98 or other suitablefastening means. The cover 88 is secured to the housing walls by a screw100 preferably threaded into a deformed portion 102. of the wall 90 andhaving a lock washer 104, or by other suitable fastening means.

A condenser 106 is removably secured to the wall 90 by 4flexible band108 that surrounds the condenser, and preferably has a clamping s/crew110 with a cooperating nut 112 for tightening the band about thecondenser. The band is secured tothe wall 90 by rivets 114 extendingthrough that wall and through deformed portions such as 116 on the band108, or by other suitable fastening means'. The. condenser 106 hasterminals 118 and 120 for making connection thereto, which terminalsproject through enlarged openings 122 and 124 respectively in thewall'90, and

are deformed so as to project into openings126 and 128 in the brackets80 and 82 respectively and make electrical connection therewith.. The

brackets 80 and 82 thus form the common connecting means towhich theconnections `to the condenser may be soldered such as at 130, 132 and134. The connections between the switch and electromagnets and the motorwindings are `made through pairs of lugs such as 136 and 138 on eitherside of the mounting member 96,- which lugs are secured to the mountingmember 96 and electrically connected by rivets or other' 4suitable means140.

mets 142 in the motor frame 144, and the lead 34 extends through asuitable insulating grommet 146 in the housing 86. The assembly thusformed by the switch, housing and condenser is secured to the motorframe 144 by mounting lugs 147 and 148 preferably formed on the walls 92and 94 respectively and'having screws or other suitable fastening means150 and l52.extending therethrough and fastening the lugs to the motorframe.

As disclosed in the embodiment of the present invention, the windings,including the main and auxiliary field windings 24 and 26 and the thirdwinding 30, are considered stator windings because wound thereon. Byvirtue of the placing or position of the third winding, that winding ismagnetically associated with the rotor and has greater magnetic couplingwith the auxiliary field winding than with the main field winding. Infact, it is effectively magnetically coupled with only the auxiliaryfield winding. Hence, there is some voltage induced in the third windingwhen the circuit to the auxiliary winding is closed, and at the instantprior to the starting of `the rotor. However, due to the magneticrelation of the rotor and the third winding, the voltage induced in thethird winding increases as the rotor speed increases, since the rate atwhich the third winding cuts the rotor flux increases with the'rotorspeed. Having the condenser 74 in series with the auxiliary fieldwinding 26 during starting, causes the current through the auxiliaryfield winding to lead that through the main field winding. Then, sincethe rotation of the rotor produces aV counter electromotive force in themain field winding, which counter electromotive force increases with thespeed of the rotor, the current through the main field winding decreasesas the rotor speed increases. Since the electromagnets 36 and .44 areconnected to the main and third windings respectively, and in fact,electromagnet 36 is connected in series with the main field winding 24while the electromagnet 44 is connected across the third winding 30, andsince the pull of the electromagnets is dependent upon the currenttherethrough, the pull of the electromagnet 36 decreases as the pull ofthe electromagnet 44 increases. The electromagnets opposingly coact upona common armature and the position of that armature is consequentlycontrolled by the current through the main field winding and thepotential across the 'third winding, and thus serves as a means ofcontrolling the starting and running circuits of the motor, whenstarting the motor, or in the operation of the motor when an overload orsome such condition occurs to appreciably change the speed of the motor.

Since the main eld winding and the electromagnet 36 are connected inseries, and to the power supply line, the pull of the electromagnet 36is directly effected by variations in line voltage. And since the thirdwinding is magnetically coupled with the auxiliary field winding, aswell as with the rotor and -since the rotor speed is dependent somewhatupon line voltage, the pull of the electromagnet 44 is dependent uponfactors including line voltage and rotor speed. The coaction of theelectromagnets t0- gether with the dependence ofthe pull of theelectromagnets upon line voltage, affords a means for compensating,within reasonable limits, for fluctuations-f,I or variations in the linevoltage.

While the form of embodiment of the present invention as hereindisclosed, constitutes a preferred form, it is to be understood thatother forms mightl be adopted, all coming within the scope of the claimswhich follow.

What is claimed is as follows:

l. A control system for a motor having a rotor and astator, comprising,in combination, a plurality of stator windings including main andauxiliary field windings displaced from each other substantially 90electrical degrees, and a third winding in space phase with theauxiliary field windings and connected to one of the field windings; astarting circuit including a reactance in the circuit of one of thewindings; a'

running circuit; a switch having electromagnets lfor controlling thestarting and running circuits and opening the circuit between saidreactance and the field winding to establish the running circuit, one ofsaid electromagnets being connected in the circuit of one of the statorwindings, and the other of said electromagnets being connected to'another of said stator windings.

2. A control system for a motor having a rotor and a stator, comprising,in combination, a plurality of stator windings including a plurality offield windings and a third winding, said third winding beingmagnetically coupled with the rotor and also magnetically coupled withone of the field windings and in space phase therewith; a startingcircuit including a reactance connected in series with one of the-fieldwindings; a running circuit; a switch having cooperating contactsconnected in series with the 'circuit of the field winding and reactancefor controlling the circuit therebetween, which contacts, when open,establish the running circuit; and electromagnets for actuating theswitch, one of said electromagnets being connected in the circuit of oneof the eld windings to effect closing of the contacts to establish thestarting circuit, and the other of said electromagnets being connectedto the third winding to effect opening of the contacts to establish therunning circuit.

3. A control system for a motor having a rotor and a stator, comprising,in combination, a plurality of stator windings including a plurality offield windings and a third winding, said third winding being effectivelymagnetically coupled with the rotor and with only one of the fieldwindings; a starting circuit including a reactance in series with one ofthe field windings; a running circuit; a switch having cooperatingcontacts connected in series with the circuit of the field winding andreactance, which contacts, when open, establish the running circuit;means for effecting closing of the contacts to establish the startingcircuit; and means responsive to the potential across the third windingfor effecting the opening of the contacts to establish the runningcircuit 4. A control system for a motor having a rotor and a stator,comprising, in combination, a plurality of stator windings including aplurality of field windings and a third winding; said third windingbeing magnetically associated with the rotor and having greater magneticcoupling with one of the field windings than with the other; a startingcircuit including a reactance in the circuit of one of the eld windings;a running circuit; a switch having cooperating contacts connected inseries with the circuit of the field winding and reactance, whichcontacts, when open, establish the running circuit; an electromagnetcontrolled by the current through one of the eld windings Afor effectingclosing of the contacts to establish the starting circuit;

and an electromagnet controlled by the 'poten tial across the thirdwinding for eecting 'opening of the contacts to establish the runningcircuits.

5. A control system for a motor adapted to be connected to a powersupply line and having a rotor and a stator, comprising, in combination,a plurality of field windings including main and auxiliary fieldwindings; a third winding niagnetically associated with the rotor, saidthird winding being connected to one of the field windings and in spacephase` with one pole thereof; a starting circuit including acondenser-in series with the auxiliary field winding, said condenser andauxiliary ield winding being connected across the power supply line; arunning circuit; and means for opening the circuit between the auxiliaryfield winding and the power supply line to establish the runningcircuit, said means including an electromagnet connected to the thirdwinding.

menos@ 6. A line voltage compensating system of motor control for amotor adapted to be connected to a power supply line, and having a rotorand a stator, comprising, in combination, main and auxiliary fieldwindings, and a' third winding magnetically associated with the rotor; astarting circuit including a reactance and the auxiliary eld windingconnected in series across the power supply line; a running circuit; aswitch having cooperating contacts for controlling the starting andruiming circuits, said contacts being connected in the circuit of theauxiliary eld winding which contacts, when open, establish the runningcircuit;- an electromagnet connected in series with the main eldwinding, and therefore aiected by line voltage, for. eiecting closing ofthe auxiliary field winding circuit; and a second electromagnetconnected to the third winding for effecting opening of theauxiliarywinding circuit, saidsecond electromagnet being responsive tofactors including line voltage and rotor speed.

CALVlN J. WERNER.

